- Positive tuberculosis (PPD) TB skin test, clinical history, and chest X-ray indicative of active tuberculosis. (Individuals with a positive PPD test and negative chest X-ray who are not symptomatic for tuberculosis, and do not require antituberculosis therapy will be eligible to participate. Participants will be asked if they ever tested positive for tuberculosis. If so, they will not be given a PPD and chest X-ray and clinical history will be used for evaluation purposes).